Kuniaki Konishi

Feb 14, 2024 | opg.optica.org | Yuki Sakurai |Akito Kusaka |Kuniaki Konishi |Adrian Lee

We developed a broadband two-layer anti-reflection (AR) coating for useon a sapphire half-wave plate (HWP) and an alumina infrared (IR)filter for the cosmic microwave background (CMB) polarimetry. Measuring the faint CMB B-mode signals requires maximizing the numberof photons reaching the detectors and minimizing spurious polarizationdue to reflection with an off-axis incident angle. Sapphire andalumina have high refractive indices of 3.1 and are highly reflectivewithout an AR coating.